To machine patterns in plate-type elements and sheets, a punching machine may be used. The punching machine includes punching tool inserts, such as punching stamps, that perform operations including, for example, stretching, bending and cutting of the plate-type elements in association with a punching die. As the punching tool inserts, e.g., punching stamps are used, they become dull or blunt, and need to be sharpened by a process called regrinding. The problem is that regrinding shortens the overall length of the punching tool inserts.
To compensate for the length of the reground punching stamps, systems are known that include multi-part punching tools that include a stamp shaft, which is suitable for use with several different punching stamps, a punching stamp centrally arranged in the stamp shaft and that can be reground, and inlay plates. Where applicable, inlay plates having different thicknesses can be inserted into the stamp shaft in a number appropriate to compensate for the variation in length of the punching stamps due to regrinding, which changes the punching stamp length.
When the length of the stamp shaft is worn down due to regrinding such that the length of the punching stamp can no longer be compensated by the insertion of plates, the stamp insert can be replaced without having to replace the stamp shaft. In addition, stamp inserts having different shapes or sizes can be used with a single stamp shaft.
A large number of tool sets may be required for economically machining sheets on punching machines given that punching is preferably performed using a single punching stroke and a separate stamp may be required for each different contour. For machining sheets having different thicknesses, dies in different sizes may be required for each stamp depending on the thickness of the sheet metal. Accordingly, tool sets may be pre-mounted to the punching machine, i.e., the tool sets are inserted in a tool magazine of the punching machine, which can increase size requirements for tool magazines.
For this reason, punching tools are used in which the stamp or machining inserts are not accommodated in the central axis of the tool. In addition, the correlation of a die of a certain size and a punching insert in the tool upper portion can be changed by twisting a tool upper portion relative to a tool lower portion. Therefore, the machine can be operated for different sheet thicknesses without remounting the tool and, as a result, punching is possible with reduced tooling effort.
A problem can arise when punching with such systems, because off-center axis stamps having different contours or sizes may each be used to punch different sheet thicknesses, such that the stamps wear down and require the replacement of expensive tool upper portions having off-center axis stamps.